In this video, host Andy discusses the topic of battery compression for lithium iron phosphate cells, explaining the reasons behind compressing cells and why it sometimes doesn't matter. The video focuses on the insights from Marcus, a battery expert who has studied electrode materials in lithium batteries. Marcus explains that compressing cells is not meant to prevent swelling and delamination, as this occurs on an atomic level and cannot be stopped by any amount of force. The actual reason for compressing cells is to squeeze out tiny gas bubbles that arise from the porous material inside the cell during the first few charging cycles. This helps improve the battery's overall performance and longevity. However, Andy also emphasizes that compression might not matter in certain cases, such as when cells are purchased from resellers who haven't compressed them during testing. In these cases, the damage has already been done and compressing them later on would not make a difference in the lifetime of the batteries.
@@OffGridGarageAustralia Just ask ChatGPT to summarize your video (provide it the youtube transcript or use a plugin) and you get exactly that description.
When I built mine 1-1/2 years ago, I used your recommendations regarding compression (none). I was getting nervous after your recent vids. Glad you sorted this out for us.
I did a lot of research when I build mine back then but information were rare. We're a bit better situated these days and have more information and also experience on hand.
@@OffGridGarageAustralia I think your newest thought about the compression sounds very logical. I imagine it's very correct. With all the practice you have now and all the extra knowledge in the world about it.😊
@RolandOfGileadOnYT Hi Roland, Markus here ;) . First of all thanks to Andy. Never thought about becoming that kind of "famous" with lauching Dominik's video :DD. Regarding your concerns about some kind of overpressure - Yes it is possible, but not with usual or non-professional tools. I have to explain it in detail: There are two sorts of expansion: The cyclic one while charging and discharging and the irreversible one caused by the effect of loosen electrode material. As I explained in that video, electrodes are compacted by calandering to increase volumetric capacity with a higher density. Especially during the first cycles the electrode is still in original shape and the expansion is caused by the intercalation of Lithium-Atoms into the Graphite-Layers. This expansion cannot being stopped. If you think about that all pairs of electrodes have a thin layer of separator between cathode and anode and this separator usually is made from a stretched foil of Polyethylene / Polypropylene you can imagine what´s the weaker part.... It´s the separator. So if you press that batttery with very very high forces and hold it constant to this distance with 100% stiffness, the force increases enormously while charging and the expansion of the anode raises until the anode penetrates or even pierce through the separator which which therafter will destroy the battery.
@@markusb69 Hello Markus, thank you for your answer. I was asking, because someone at the DIY Solar Forum asked about this, he had the impression he compressed the cells to the point where the (short) side of the case buckeled inwards ever so slightly. I myself have a battery with plywood on both ends and threaded rods, and compressed/locked the cells in place (there's a insulation between cells), until I couldn't move the cells anymore. Afterwards, I wondered if I should have made the blue cell wrapping somewhat less slippery first, so the cells would be fixed in place with somewhat less force. The corners of the case still don't touch eachother. But from reading your answer, I'll take it that as long as you don't truely crush the aluminum casing, you should be fine, cause the stuff we use to hold the cells won't be strong enough to withstand the forces that cause this minor expansion during cycling?
Two possible scenarios I think a fixture (not necessarily compression) could be a good thing. I built two 48v batteries 1 year ago, one of them is installed in my boat - I wanted to minimise damage caused by vibration. The other battery is running my house. The key thing here I used flexible bus bars on both batteries between all cells to allow small movement due to vibration and swelling. I was more concerned about any movement damaging the cell terminals / electrodes.
If the bus bars are long enough, there will be a gap between the cells and therefore, the tiny swelling will not cause the cells to touch each other or apply any force on the terminals. So flexible bus bars aren't necessary in that case. And as Andy said, it's good to have some space between cells for ventilation to keep their temperature lower - assuming the load current is high enough to raise their temperature significantly enough to need the ventilation.
An NKON company representative recommends compression. I don't think it can get any worse. Or better yet, questionable. I do the compression with two metal plates and four 8mm studs. Self-soothing is a great thing! Thank you for the video. Oleg, Ukraine.
Hey Andy, great you used that fantastic Interview video. What is missing now is the aspect of connecting the cells. Bus bars are rigid whereas cables connect the cells in a flexible way and can compensate the breathing of the cells …
I love how people get so beside themselves because we don't do what they think we should do. Andy you do you! And if no one likes it oh well. I love ya!!! Keep doing you!!!
Danke Andy für kurze und gute Erklärung. Dann bin ich auch beruhigt und werde an meinen akkus nichts ändern und mir keinen Kopf zerbrechen. Top Videos mach weiter so.
One obvious benefit from compression is that you fix the whole assembly to avoid stress on the busbars,and you are right,for this you don't need much force, the assembled batteries in a PE casing does the job
yea he didn't even mention it. But the bus bars don't matter, the things they are connected to do (anode/cathode terminals) If you build the batteries directly touching and straight bus bars it'll damage the anode and cathode terminals. best is the leave a say.. 2mm gap between the cells or something if you aren't going to put something between it. at least they will last then
I have compressed my 15 x 280ah EVE Batch Matched cells since I bought them, the where perfectly square. Had to take them apart and saw they have expanded indeed after a year. Why did I take them apart? Added 3 more for a 18 cells bank (3.45v x 18 = 62.1v) ... I can because I use Victron equipment. 🙂 Max volts on a 48v system is 66v.
@@FutureSystem738 Just make sure that your BMS can go that high on volts. I use the JBD 20-cell one. Just had to rewire the balancing leads for 18 cells from 15.
@@i.do.not.exist.9992Yep, it’s a great idea and if everything adds up and can handle it (BMS, Charger, Victron inverter) then why not? I really like the idea!
Thanks Andy. Another great, informative video. We just can't stop learning from you. What are we going to do if/when a new battery chemistry is introduced? Can't wait! Fun fun fun or spat spat spat😊
I Compress my cells for one reason...ease of handling. I do this with 12v 4 cell builds. I use the compressed cell battery in small mobile setups. I use 4" electrical tape to do this and makes the cells easy to handle like the format of a lead acid car battery. 😊
Great one Andy, answers a LOT of questions. We’re all still learning about these cells, and probably will still be in 30 years, (though based on family history I won’t be here then.) However in the meantime, I’m still planning to be here anyway. Maybe I can beat the odds, and maybe my batteries will also still be going. 😁
Thank you so much for your informations aboute compress cells or not. My research has revealed the same. And thank you for your very informative videos! Greetings from Sweden...
Andy... i dont have a lot of money and i just received my first 8 lifepo4 and the other 8 should be here in a few days. Im building a 560 ah eve battery with grade a cells. I need my batteries to last as long as possible and i appreciate the work you do and all the videos. Hopefully they last a long time and give me and the wife years of off grid life.
Great information Andy! Love it and thank you for sharing!!! I have not heard some of that! You are 100% correct how some of those places test there 1000 cells at a time. I was sent a similar video and pictures when I purchased mine lol. I would like to add one benefit of compressing or fixing a group of cells. The accidental or unintentional overcharging of a cell or cells from a faulty bms or whatever the reason. You can prevent the pack from making a smiley face😀which may help from damaging other cells and depending on the area the cells are in could prevent damage to other equipment. Dont mind me, I over think EVERYTHING!! 🙄
Great and powerful research! Greetings from Ukraine, I am just getting ready for winter shutdowns and will build my lifepo4 battery. Your videos help me a lot with this
Great stuff! For me now... what becomes more of a concern when putting together a battery bank? I'm thinking that a solid connection (Bus bar) between positive and negative between each battery could be a point of failure over time, as the natural expansion and contraction happens with the cells and pulls on the terminals of the battery. I believe that a space between the cells to begin with should be a good start, then using an expandable electrical connection between the posts should be even better. (Like what maddie the mermaid uses). 🍻
Compression prevents unnecessary expansion. Yes some expansion is not able to be prevented. Excess unnecessary expansion can cause delamination. I use springs to keep the cells constantly close to the proper compression. Overcharging or overdischarging causes delamination. Proper compression can stop excess expansion during those mistakes. That’s why the manufacturers of the cells recommend a specific pressure
Another great video, one of your best Andy. Fixture IS important, but no, you don't have to do it. Cycle life might not be important in your high capacity installation, but most DIY installations are on a budget, and cycle way more then you do. My marine customers usually do a 600AH 12vdc installation that gets a full cycle every day or two. These installations average 250 to 300 cycles a year for my commercial customers that recharge with a diesel generator or shore power (no solar). You brought up something I'm pretty sure I failed to mention in my previous explanations. The cells do in fact swell and compress. Like I motioned in previous comments, the major swelling you've experienced is avoidable with a fixture, it's why I said that cells should only be removed when empty. The level of swelling you've experienced is completely avoidable. As for your statement that cells won't be damaged by compressing after they have severe swelling, my friend I encourage you to do so and see for yourself the fluid flowing out of the seal( It will make a great video =). Fluid breaking though the seal is damage. The question then becomes, how much damage can be done before cell capacity is affected? I personally have have not been willing to push past the seal breaking point after doing it the first time. If you flatten them until they are as flat as new cells will they burst and compromise the vacuum? inquiring minds want to know. Lets see that video Andy! For Science!!1
Wow, yes, that would make a great video! 😮 I have Winston cells in my RV that I assembled with significant compression, and flexible Busbars. To my knowledge they’re still virtually as good as new. Although I haven’t disassembled the pack (big job in a tight space!), nor done a full scientific capacity test, I have noticed zero problems with daily use and the occasional deeper discharge, and they are still absolutely fabulous. I also have a friend who has “abused” his a lot more than me, with some low voltage AND high voltage “excursions”, with no BMS. They’re also still fine.
Hi, I bought some 20 year old winston thundersky 60ah, Capacity is 50ah, so calendar ageing is pretty slow, they were factory compressed in 3 cell packs.
Thanks Andy for the reassurance on my decision not to compress for my 12v 280ah pack I made. I cycle it aprox 12 times per year so it will make 0 difference for me.
Thx for the video. I built a clamp for initial testing my cells after reading that manual - not made of out metal, but out of "18mm Siebdruckplatte", and i do not exactly compress to 300kg. Well - first cell of eight i tested without that clamp, all the other cells with clamp. And i have to admit: the first cell got a little more bloated then the others - not really exactly measured it, but you could see the slight difference. Cells were nearly perfectly flat before testing (EVE LF280K Grade A Cells from NKON). Well another aspect: when you compress flat cells with a force of 300kg and cells will expand anyway (on that atomic level), the pressure might rise above 300kg leading to damaging the cells 🤔? Not sure about that, so i do compress my cells a little using a compressed sturdy closed foam piece that can expand when pressures rises. The video is definetly worth watching - and stills leaves some unanswered question :). I'm curious when there will be a followup.
Thanks Andy. I am though, going to replace the busbars with flexible cable and lugs as I do believe that there is stress on those terminals. And I dont think that will do any battery any good. Luv ya effort.
Congrats! Your are the first I watch who has gotten it and explained it in a very clear way. Remains the question what would have happened to your "certified" cells which spread apart. I think it helps to keep the cells in check so no readjustment of solid bars is necessary. If you have flexible busbars then it might not matter. So there might be a mechanical advantage to apply some pressure to the cells.
I developed a way to administer the right amount of compression to the cells with my cordless screwdriver. I didn't want to buy another tool (torque wrench) which I would use only one time. So I thought about the screwdriver I already own because its torque can be adjusted. Albeit with no calibrated settings. To find the right setting I used bathroom scales and a lever. The lever was attached to a board at one end with a long screw. Halfways I made a hole in the lever and the board through which I put the actual threaded rod I want to use on the battery. The far end got a short screw which pressed on the scale. So I had a 1:2 ratio of the middle and the end forces. The 300kgf on the battery cells will be achieved by four tensioning rods. So a single rod has to produce 75kgf of pull. On my setup if the 75kgf have been reached at the middle of the lever the scale would show 32.5kg. I let the cordless screwdriver tighten the nut on the rod until the scale showed 30kg. Then I turned the clutch setting back until it clicked (released) at that scale reading. I marked the setting and that gave me the torque wrench setting I need.
Hello ! I have started to build my own 12v battery after I have seen all your videos from the beginning until now. It is a small project but I am learning. Congratulations for all your good work and good advices! You are the best !
Your explanation sounds solid and clear. But you state positions so strictly that i ask how can you be sure? I could imagine that a compression even after some testcycles done in the factory could still prevent damage by even more little bubbles or at least it will help get the bubbles out of the active material. To me it all sounds more like guessing and try-and-error process what treatment is most beneficial. I agree the effort of compression might not pay out over time because the cells degrade more from aging than from cycling in a typical usage.
@@OffGridGarageAustralia agree - but is that a problem? Its better for the capacity if the layers are kept closely together. Problem is the cell needs to 'breath' a bit, a y-bit.
But you didn't mention anything about terminal stress. Your batteries in their swelled state appeared to be put some stress on the terminals. Also I've had my Eve 230 cells compressed since I bought them 18 months ago and I will take them apart again this weekend to check with a straight metal ruler for swelling. But I did not see any last weekend when I had them apart for reconfiguration
Almost two years ago I had a translated conversation in China with a CATL rep. I was told that the main enemy of Lifepo4 cells is moisture, and that a deep vacuum is applied to the cells prior to sealing in order to convert any moisture into a gas, remove as much moisture as possible, and that any remaining moisture in gas form was not expected to cause damage The compression I was told was to help maintain cell vacuum and keep any moisture present, no matter how little, in gas form where it will cause no damage. So, now I have even more questions. Actually, questions upon questions which lead to even more questions. Given that spent time is the only thing which we can never recover, I'm ready to move on.
Yeah- I’m sure we will know a lot more about these cells in thirty years time. Problem is: I won’t still be here 😅 It’s all still fascinating though, great stuff and great research and testing by Andy. At least my seven plus years old LFP Winston cells are still awesome.
@@FutureSystem738 I realize that this is an old comment, but on the off chance that you may see this and reply: I have been highly interested in these Winston cells, yet I have been unable to find much info on them in terms of real world experience. You have that, so if you might kindly answer a couple of questions I'd be greatly appreciative: 1) In what application are you using the Winston cells (ESS, EV, mobile/marine, etc.)? 2) What size cells do you have? What is your pack voltage, and in what configuration are they assembled (i.e. 16s1p, 8s3p) What really intrigues me about them is the manufacturer's claim that the Winston batteries, due to the yttrium, can be safely charged in low temp environments that far exceed that of a typical LFP battery. Any info you can offer is greatly appreciated. Thanks in advance!
@@vastirvision My Winston cells are 400Ah cells in just a 4s (ie: 12v) configuration in my large caravan. I built the pack at the beginning of 2016, and for many years operated them without any kind of BMS, just keeping a bit of an eye on balance with individual cell voltage monitoring, and using very conservative voltages to avoid any chance of a cell going high, and typically 13.8v top of charge = 3.45v/cell. (They’re bolted in to the caravan under some degree of compression.) I actually manually balanced them slightly maybe about three?? times. Then I added a JK BMS a year or so ago, which keeps them extremely well balanced, usually to within 2 millivolts, and as a result I upped the top of charge to 14v = 3.5v per cell. Although I have never FULLY capacity tested them since installing, I often discharge to about 20% and have noticed no capacity loss since the beginning of 2016. I have about 1kW of solar, and we use them for everything including hot water, fridge, induction cooker, microwave, and even some airconditioner use (heating and cooling) when solar conditions are good. If the weather is not so good, we revert to using some LPG for hot water and cooking to reduce electrical demands. I was not aware of any claims about charging at lower temps- have always avoided any charging if they’re close to 0 Celsius.
Firstly; thanks for your fantastic input (output?) Andy…. Secondly; I’m trying to commission (!) a 16S set of 340Ah cells before Xmas and struggling to see see through the miasma! I am now a bit more relaxed about it but there is one thing that strikes me: How does one apply 300kg of force to a battery pack?!?!?! Mine are envisaged to be organised in two rows of 8. That’s therefore 600kg over the two faces. Incredible! I had decided to use threaded bars in conjunction with flat plates of currently unknown dimension and material and spring load the bars with old engine valve springs, to prevent exponential pressure changes as the cells wax and wane, but now I’m not convinced that my springs are man enough.
Great video. Thanks for sorting that one out. However.…., You still might want to “compress” your batterie cells for mechanical reasons. Assuming that some stationary batteries are going to be moved around, especially by DIYers, a form of mechanical fixing might be a good idea. Packed with EVA foam in between the cells, EVA foam will compress as the battery cells expand. The cells will more likely maintain their position and this will reduce the stress on the busbars and terminals.
Thanks for sharing Andy, now I have another channel to watch as well 🤔, you made good points. I think I like your option of spacing between cells as your busbars won't get tense by the expansion of cells. Keep the sunny side up down under!
Apart from the arguments regarding cycle and aging of the cells, would not compressing (eg fixing ) them make sense to keep the busbars in position ? Or is it actually the other way round, always leave a bit space between the cells for the ‚swelling‘ so that there is no impact on the busbars ? ( not a option in campers / boats )
Like Andy said, you cannot stop the expansion. Nothing on this earth can stop the expansion. So, something has to give! If the cells are compressed, I think you do more damage to the battery terminals under a tremendous amount of physical stress.
So what you are saying is that I should compress my cells for the first couple cycles (I basically got them directly from EVE without any further charging/discharging) to press the gas bubbles out and then keep them kind of uncompressed (my chinese case has some form of compression built in(
Interesting video. Good job that my compressed cells are EVE grade a cells, from a supplier I trust. I also didn't test or charge them until they were compressed. Mine are cycled every day or two.
I believe that the manufacturers would be the experts on their cells. If they say it's better to compress, then that's enough for me. We all are amateurs compared to the experts that design the cells.
Thanks Andy - between this video and the other one you linked to, you've laid out a lot of great info. I can now see how compression won't make a difference in my use case!
Agreed, although based upon Digital Mermaid's heat tests of rigid vs. flexible bus bars, I think the verdict is in that flexible is better all around if you're willing to put the work in to construct them.
But, what about the cell terminals? If the expansion pushes the cells apart by even 5mm per cell, won't that mean that a row of 8 cells has the potential to expand by around 40mm in total? Busbars with with low tolerances might therefore cause pressure on the cell terminals and damage them as a result. I think light compression (using Kapton tape perhaps) could help in this regard. It also helps keep the battery together in the event of an earthquake too. 😉 Love your show btw.
That's been really interesting. Thanks for sharing. Any we have to understand, that when that another of cycles the batteries are still at 80%. No reason to throw them away if you ask me. And I love you too, Andy😘
I just checked my Victron Connect BMV-700 [Google -> Upgrade ostrovní elektrárny 12-36kW, LiFePo4]. It let me know, that for the last 16 months (Jan-2022 I installed BMV-700) I did 13 total charge cycles. So in my case, for 2500 cycles I have to charge/discharge my cells for 256 years. Well I am fine with these numbers.😀. Thank you Andy, you are great!
Brilliant !! Could also be titled " The debate around A & B grade cells...and why it doesn't matter". A suggestion for follow on video. What things really matter for a long lifetime from you LPF batteries..
As others have said, the movement of uncompressed cells can cause stress on the terminals. I setup 16 eve 280 cells uncompressed and after about 20 cycles the noticeable swelling on about half the cells (interestingly it was not even) was pushing the bottom of the cells apart due to the clamping force on the terminal. They are now clamped with braided bars! Separately, Mine do one full cycle per day. If uncompressed means I only get 2500 cycles, that is under the 10year calendar life and crosses over to the point where compression could extend the useful life????
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Personal experiment over a three year span: LiPo cells not lifepo4 but close enough for the comparation. The packs consisted of six 8Ah cells. There were two packs. All exterior (outer) cells swollen with age and gentle, much below specifications. Cells were specified to run from 3.5v to 4.20v at 15C. I used them within the voltage range, strictly, and peak currents were below 4C, mostly below 1C. All four cells that were on the outside of the packs are swollen, lost their capacity beyond usefulness but the interior remaining cells that were kept compressed inside are still above 80% capacity and not swollen.
I have gone through 100's of lipos cells over the years flying RC airplanes, helicopters, and FPV drone racing. Some I have flown even swelled they still continue to work I use them until they will not hold a charge swelling doesn't concern me. The only batteries I won't fly is if they were smashed up in a crash. The few I have seen catch fire while charging always were involved in a crash. Lot depends on brands not all that cost lot more made a difference. Some cheaper brands sold from hobbyking worked well others didn't .
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@@Mike-01234 flying an rc with fluffy lipos and riding fluffy lipos ain't quite the same. Alright, it hurts when crashing and burning an expensive model but it hurts more when crashing and burning an EV or a house with your arse in it :)
Hmm, I think the unavoidable swelling you mention around @2:35 is well known. As you charge the cell expands, as you discharge the cell contracts. I think that is different from the cell gradually getting a larger "Beer Belly :)" overtime. The question is, will your cells keep expanding? A year from now, will they be even more swollen. Would be interesting if you kept records of the sizes overtime. Thanks for the video!
All cells will expand at the beginning to a certain point. Only if you overcharge the cell, it will expand further. The expert also says, don't go near the 2.5V or 3.65V mark as the cathode and also the electrolyte start decomposing which causes damage and the cell loses capacity. 2.75V - 3.55V was recommended.
@@OffGridGarageAustralia Great news! My caravan LFP cells, over 7 years old, have never been below 3 volts and been briefly above 3.5 volts maybe just two or three times in total. Normal for my cells is 3v absolute minimum to 3.45v absolute maximum. The little you gain by going further is negligible capacity gain for much more stress.
@@OffGridGarageAustralia Totally agree Andy. 👍 Our car has been above 90% maybe three or four times, and above 95% literally NEVER. It has also been below 20% maybe four times as well, and below 10% NEVER.
Graphite expansion from zero to 100% state of charge is about 11%. Graphite is about 20% of cell volume. 11% of 20% is only a bit over 1 mm thickness change on 70 mm wide cells. Most of what folks call bloating is excessive electrolyte decomposition. It creates the gas that bloats the cell, but the real damage done is the electrolyte solvent that decomposes to hydrocarbon tars that are left behind clogging up the electrode and separator pores restricting lithium ion exchange. Overcharging is usually the most common cause of electrolyte breakdown. The cell wrap is open at terminal top end of laminate wrap so most of the gas escapes into the metal container which is what is bloating, not much bloating on actual laminate wrap. Initial charge forming by manufacturer builds the protective SEI (Solid Electrolyte Interface) layer around negative anode graphite granules. This breaks down and consumes some of electrolyte and creates a significant amount of out gassing. The vent port is last thing placed on cell casing so most of this charge forming outgassing escapes before port seal is installed. Normal use charging cracks some of the SEI protective shell due to graphite expansion and it is repaired on subsequent recharging. It does consume some of the electrolyte and available free lithium causing degradation of cell over time. It also thickens the SEI which increases cell impedance. It is part of normal aging process. Nothing to do with compression. Delamination damage is mainly the separation of graphite and LFP electrode from copper and aluminum foil current collector. Chance of delamination increases when cell temp rises due to high discharge/charge currents and ambient temps. At
Well, this is interesting as well… it’s hard to shift mindset from compression to no-compression though. You made it clear that it’s impossible to prevent the expansion of these cells. There is no hydraulic press large enough to prevent this, right? What I’m not quite getting though is, with all these people building packs with static compression designs and a variety of collection of cell number, wouldn’t we be hearing about static compression cases breaking? If each cell expands by a few mm, the whole pack can grow quite a bit depending on the configuration. If a 2P4S pack grows by 16mm, I doubt the steel rods holding them together would survive that, or the wood. As a matter of fact, sounds like it’d be quite dangerous! It just seems strange that we don’t hear about compression frames failing, or even signs of failure (though it’s possible I totally missed that). If that expansion is inevitable, then something in these compressed designs has to give…
Oh, no, I don't want to shift any mindsets here! This is just for pure information purposes. And the cells will not expand by a few mm. It is less than 1mm usually, if at all. And yes, wrong compression can be in deed dangerous. The cells will eat this movement internally if the outside compression is too large. Most people use some sort of plywood or plastic for the compression, so this material is some sort of 'soft' anyway.
From a CATL datasheet : "The cell will generate swelling force during attenuation. The swelling force of the cell at 60% SOH under the test condition of 15mm steel plate, which is about 40000N. The customer needs to consider the reliability of structural strength in the product design process." I'd say yeah, that is heaps of force. If I did the maths right, thats 1100kPa or 160PSI. Likely more since I used the entire surface area of the side of the cell (280AH) since it was not indicated. Kind of crazy. Looking at the construction of various batteries (from those with no compression, to those with squishy foam pad things, to those banded with steel and heavy steel plates at each end) I reckon I really like the idea of squishy rubber padding between the cells, with some compression from either steel banding or threaded rods. Gives some pressure, but has give too. Only time will tell, for first hand experience for me. I've only just gotten into the LiFePO4 game.
I have six different (compressed) packs in operation. All cells are isolated, 2mm cork, 240g/m^2 waxed paper and 2mm foamed plate material. The foamed material looks best and the + - 1mm expension during charge / discharge appear perfect compensated. My next packs will by in the same way!
well done Andy! I retain my cells, which looks a lot like compression, because I my solar cells are mobile. and shaky moving cells is bad. I think this is a valid case.
Andy thank you for this video! It has really helped. I was getting so much contradicting information and was just confusing. This is a really solid explanation
Andy, if you were using the cells for vehicle propulsion, discharging over say 4 hrs then charging 4 hrs, again and again, then the number of cycles would be vital wouldn't it? Hence compression from day 1 seems to be best. But... as you ask, it only needs to be for a "few" cycles. Thank you for your great vids!
The reasons that you listed I would not compress a cell for. Why I would compress a cell is I don't want the terminals to be shifting in applying pressure. Just like you did when you check your battery rack you readjusted the gapping. There's two ways of doing taking yourselves apart and adjusting them every so often or just clamp them down so they don't shift.
Bitte nicht auf den Blödsinn von Andy hören. Der verbreitet so viel falsches, nur um Klicks zu bekommen. Es gibt sehr viele gute Gründe, die Zellen mit Kompression einzubauen. Andy hat leider wenig davon verstanden. Aber dies ist ja bei seinen Videos üblich. Jeder lernt, manche eben nur mit Try-n-error...
Put your cell on a vibrator and any bubbles that are stuck will rise to the top 😁 Like the needle vibrator for the concrete used to remove the bubbles inside the concrete. I'm pretty sure, none thinked about that.
Yeah, the expert said it would need a vacuum and around 400°C to remove them all but at these high temperatures the separators (PP material) will not survive.
I‘ll not use compression at all. The cells will survive or not. I have seen compressed cells exploded for improper charging. That is the thing to be aware of. Some ppl do not see the bms as a part of the battery and put a breaker in the wrong place or dont use a bms at all, what will kill some cells of the pack sooner or later. My awareness will be temperature in wintertime, my battery place is an unisolated shelf outside the house, so I‘ll isolate the batteries and put some heating elements inside, to keep the cells above 5 Celsius. Thanks for your video. We are the rare ones without compression. And what I see in many videos, they do compression without feathers, so its wrong and the force rises while charging and that is a lot.. better no compression than wrong compression.
Great video Andy. I think you should put compression on the top shelf of the battery 1.0 and leave the other two shelves without compression. In 33 years we will know which lasted longer. 😂
I think you have hit the nail on the head here. We don’t have actual evidence of what these cells will be like in 33 years. Everything is hypothetical.
@@chrispaul7401 Whilst different in that they have a plastic case, my Winston LFP battery in my caravan (12v/400Ah) is still absolutely fabulous after well over seven years, so that’s a great start. Will they still be around at 30 years of age? I doubt it, but likely neither will I. 😅
Anode builds its SEI over the first five cycles, most of it during the first couple cycles. It is the manufacturer charge forming process. This should be complete before end user receives cells.
That can’t be the hole story. Your cells are/were swelling. That should mean that they are changing within. I’m not saying it is bad, but as you noticed; It will create problems with the busbars. Did they say anything about that? ( Happy you still want me to enjoy your channel even though I do compress my cells 🤪)
No words about the connection or bus bars. I guess it comes down what kind of setup you have, mobile/stationary. To be sure, you can just use flexible bars or make your own cables. My cells are perfectly fine. The swelling is really minimal and is almost the same as brand new certified cells I have tested.
I wonder during expansion with each cells connected with solid busbar, would there be sufficient pressure from the expansion to break or damage the positive and negative terminals
Yeah, that could be the case! When I decided to not compress, the main reason was to allow airflow and cooling. But now with all we know, it seems to be beneficial as the cells can do whatever they want and the busbars stay as they are.
I have a 32AH 8S LIFEPO4 battery. Rectangular cells. Not compressed. Put in service. For the first year all was good. Then I left it alone with a trickle charger for 6 months (the BMS should have shut off the charge when fully charged). I came back and they were hugely swollen. Probably 4mm per cell. And blew apart the battery box. No apparent damage to the lugs. Can they be recompressed (to fit back in the battery box) and put back in service?
Представитель компании NKON рекомендует компрессию. Я не думаю, что может быть хуже. Или, что еще лучше, сомнительный. Я делаю компрессию с помощью двух металлических пластин и четырех 8-миллиметровых шпилек. Самоуспокоение - это здорово! Спасибо за видео. Олег, Украина.
Would it not be useful to "compress" cells to make sure that the busbars do not put too much stress on the terminals, or cause bad connections? Which is mitigated when you reconnect the cells, but for welded busbars this does become relevant i imagine. Putting some isoprene between the cells does mitigate this, as the isoprene would make sure that some space is left between the cells and takes up the swelling, and keeps the cells in position with respect to the busbars.
I'm going to agree to disagree on this one. I wish I wasn't under NDA for some of these aspects, but I've seen the difference first hand in my lab which included X-Ray/Neutron imaging of the cells to determine intercalation, morphology changes and degradation processes. Look up "4D imaging of lithium-batteries using correlative neutron and X-ray tomography with a virtual unrolling technique" and search 'compression' in that article. That was a study from 2020 in Nature.
Two big questions behind : i) "How many cycles to extract all gaz bubbles vs how many cycles resseller are doing for testing". I a pretty sure the ratio is > 1... ii) If we can't avoid expension whatever compression or not, but what abbout the rate of expension with or without compression....
In this video, host Andy discusses the topic of battery compression for lithium iron phosphate cells, explaining the reasons behind compressing cells and why it sometimes doesn't matter. The video focuses on the insights from Marcus, a battery expert who has studied electrode materials in lithium batteries.
Marcus explains that compressing cells is not meant to prevent swelling and delamination, as this occurs on an atomic level and cannot be stopped by any amount of force. The actual reason for compressing cells is to squeeze out tiny gas bubbles that arise from the porous material inside the cell during the first few charging cycles. This helps improve the battery's overall performance and longevity.
However, Andy also emphasizes that compression might not matter in certain cases, such as when cells are purchased from resellers who haven't compressed them during testing. In these cases, the damage has already been done and compressing them later on would not make a difference in the lifetime of the batteries.
Jeeeez, I should copy and past this in my description of the video...
Or use it as a script for a 1min long video instead of 12min 🤔
@@OffGridGarageAustralia Just ask ChatGPT to summarize your video (provide it the youtube transcript or use a plugin) and you get exactly that description.
@@OffGridGarageAustralia used gocharlie
So you're saying that even if I compress my cells they could still possibly become bloated enough to cause an air gap if pushed too hard?
Thank you for compacting it, you saved me several minutes.
I gave my cells a big hug when I got them and hopefully that squeezed out all the bubbles. I compress them with my love.
What the hell man 😂
That's the way, Brian. Great!
😅😅😅❤
I did the same, you’re not alone!
Did your wife get jeolous?
When I built mine 1-1/2 years ago, I used your recommendations regarding compression (none). I was getting nervous after your recent vids. Glad you sorted this out for us.
I did a lot of research when I build mine back then but information were rare. We're a bit better situated these days and have more information and also experience on hand.
@@OffGridGarageAustralia what about 'overcompressing'? Does that exist? Or will the compressing wood/steel/etc, still expand a little?
@@OffGridGarageAustralia I think your newest thought about the compression sounds very logical. I imagine it's very correct. With all the practice you have now and all the extra knowledge in the world about it.😊
@RolandOfGileadOnYT Hi Roland, Markus here ;) .
First of all thanks to Andy. Never thought about becoming that kind of "famous" with lauching Dominik's video :DD.
Regarding your concerns about some kind of overpressure - Yes it is possible, but not with usual or non-professional tools.
I have to explain it in detail: There are two sorts of expansion: The cyclic one while charging and discharging and the irreversible one caused by the effect of loosen electrode material.
As I explained in that video, electrodes are compacted by calandering to increase volumetric capacity with a higher density.
Especially during the first cycles the electrode is still in original shape and the expansion is caused by the intercalation of Lithium-Atoms into the Graphite-Layers.
This expansion cannot being stopped.
If you think about that all pairs of electrodes have a thin layer of separator between cathode and anode and this separator usually is made from a stretched foil of Polyethylene / Polypropylene you can imagine what´s the weaker part.... It´s the separator.
So if you press that batttery with very very high forces and hold it constant to this distance with 100% stiffness, the force increases enormously while charging and the expansion of the anode raises until the anode penetrates or even pierce through the separator which which therafter will destroy the battery.
@@markusb69 Hello Markus, thank you for your answer. I was asking, because someone at the DIY Solar Forum asked about this, he had the impression he compressed the cells to the point where the (short) side of the case buckeled inwards ever so slightly.
I myself have a battery with plywood on both ends and threaded rods, and compressed/locked the cells in place (there's a insulation between cells), until I couldn't move the cells anymore. Afterwards, I wondered if I should have made the blue cell wrapping somewhat less slippery first, so the cells would be fixed in place with somewhat less force. The corners of the case still don't touch eachother.
But from reading your answer, I'll take it that as long as you don't truely crush the aluminum casing, you should be fine, cause the stuff we use to hold the cells won't be strong enough to withstand the forces that cause this minor expansion during cycling?
Great Video!
I especially liked the part that you watched the my video several times ;-)
Here is the man himself. Thanks for the video and information. It was a great show!
"Der Drops ist gelutscht" - so nice.... Thank you and many greeting from rainy and cold germany, Wolfgang
Two possible scenarios I think a fixture (not necessarily compression) could be a good thing. I built two 48v batteries 1 year ago, one of them is installed in my boat - I wanted to minimise damage caused by vibration. The other battery is running my house. The key thing here I used flexible bus bars on both batteries between all cells to allow small movement due to vibration and swelling. I was more concerned about any movement damaging the cell terminals / electrodes.
If the bus bars are long enough, there will be a gap between the cells and therefore, the tiny swelling will not cause the cells to touch each other or apply any force on the terminals. So flexible bus bars aren't necessary in that case. And as Andy said, it's good to have some space between cells for ventilation to keep their temperature lower - assuming the load current is high enough to raise their temperature significantly enough to need the ventilation.
An NKON company representative recommends compression. I don't think it can get any worse. Or better yet, questionable. I do the compression with two metal plates and four 8mm studs. Self-soothing is a great thing!
Thank you for the video.
Oleg, Ukraine.
Привіт, підкажіть як ви досягаєте необхідної сили стискання ? Дякую
Hey Andy, great you used that fantastic Interview video. What is missing now is the aspect of connecting the cells. Bus bars are rigid whereas cables connect the cells in a flexible way and can compensate the breathing of the cells …
I love how people get so beside themselves because we don't do what they think we should do. Andy you do you! And if no one likes it oh well. I love ya!!! Keep doing you!!!
Love you, bud! 😉
Danke Andy für kurze und gute Erklärung. Dann bin ich auch beruhigt und werde an meinen akkus nichts ändern und mir keinen Kopf zerbrechen. Top Videos mach weiter so.
One obvious benefit from compression is that you fix the whole assembly to avoid stress on the busbars,and you are right,for this you don't need much force, the assembled batteries in a PE casing does the job
yea he didn't even mention it. But the bus bars don't matter, the things they are connected to do (anode/cathode terminals)
If you build the batteries directly touching and straight bus bars it'll damage the anode and cathode terminals.
best is the leave a say.. 2mm gap between the cells or something if you aren't going to put something between it. at least they will last then
Thank you for helping my upstairs to function better... good research and reporting.
I have compressed my 15 x 280ah EVE Batch Matched cells since I bought them, the where perfectly square.
Had to take them apart and saw they have expanded indeed after a year.
Why did I take them apart? Added 3 more for a 18 cells bank (3.45v x 18 = 62.1v) ... I can because I use Victron equipment. 🙂
Max volts on a 48v system is 66v.
Interesting (great!) idea. I’d never thought of doing that, going higher on voltage.
Hmmmmmmm.
@@FutureSystem738 Just make sure that your BMS can go that high on volts. I use the JBD 20-cell one. Just had to rewire the balancing leads for 18 cells from 15.
@@i.do.not.exist.9992Yep, it’s a great idea and if everything adds up and can handle it (BMS, Charger, Victron inverter) then why not?
I really like the idea!
Thanks Andy. Another great, informative video. We just can't stop learning from you. What are we going to do if/when a new battery chemistry is introduced? Can't wait! Fun fun fun or spat spat spat😊
Learning will never stop for us, I guess. Oh a new chemistry??? What may that be?
Nickel-Iron battery ?
@@M-Clem Can you buy single cells already or is this still future?
Great breakdown on this issue where nobody could really give a clear answer. Happy to see it put to rest.
I Compress my cells for one reason...ease of handling. I do this with 12v 4 cell builds. I use the compressed cell battery in small mobile setups. I use 4" electrical tape to do this and makes the cells easy to handle like the format of a lead acid car battery. 😊
one of not so many channels that really deserves subscription
Great one Andy, answers a LOT of questions. We’re all still learning about these cells, and probably will still be in 30 years, (though based on family history I won’t be here then.)
However in the meantime, I’m still planning to be here anyway. Maybe I can beat the odds, and maybe my batteries will also still be going. 😁
Thank you so much for your informations aboute compress cells or not. My research has revealed the same. And thank you for your very informative videos! Greetings from Sweden...
Thanks for your feedback and hello to beautiful Sweden 👋
Thanks for picking this up Andy
This topic pops up again and again.
Andy... i dont have a lot of money and i just received my first 8 lifepo4 and the other 8 should be here in a few days. Im building a 560 ah eve battery with grade a cells. I need my batteries to last as long as possible and i appreciate the work you do and all the videos. Hopefully they last a long time and give me and the wife years of off grid life.
Finally, a definitive answer on this subject. Thank you so much!!
Brilliant, Andy! We should discuss Warp Drive someday. I think your insights would be valued. I hope you enjoyed the beer!
And whether you compress your cells or not, we always love you Andy
I love you too, my friend!💖
Great information Andy! Love it and thank you for sharing!!! I have not heard some of that! You are 100% correct how some of those places test there 1000 cells at a time. I was sent a similar video and pictures when I purchased mine lol. I would like to add one benefit of compressing or fixing a group of cells. The accidental or unintentional overcharging of a cell or cells from a faulty bms or whatever the reason. You can prevent the pack from making a smiley face😀which may help from damaging other cells and depending on the area the cells are in could prevent damage to other equipment. Dont mind me, I over think EVERYTHING!! 🙄
Thank you. I did not compress and run an oven on my 24v system at .5c and the cells are happy. Not that much swell but all is well.
Not that much swell but all is well. 😂
Great and powerful research! Greetings from Ukraine, I am just getting ready for winter shutdowns and will build my lifepo4 battery. Your videos help me a lot with this
You should have all the info here on the channel. Take care!
Great stuff!
For me now... what becomes more of a concern when putting together a battery bank? I'm thinking that a solid connection (Bus bar) between positive and negative between each battery could be a point of failure over time, as the natural expansion and contraction happens with the cells and pulls on the terminals of the battery.
I believe that a space between the cells to begin with should be a good start, then using an expandable electrical connection between the posts should be even better. (Like what maddie the mermaid uses). 🍻
@@davidb.5544 Yes, those would be great as well!
Compression prevents unnecessary expansion. Yes some expansion is not able to be prevented. Excess unnecessary expansion can cause delamination. I use springs to keep the cells constantly close to the proper compression. Overcharging or overdischarging causes delamination. Proper compression can stop excess expansion during those mistakes. That’s why the manufacturers of the cells recommend a specific pressure
Dan, also what will happen in batteries which have welded busbars (QSO for example)...?
@@OffGridGarageAustralia Right!, Good point!
@@OffGridGarageAustralia Just about all welded bus bars I have seen have had the hump in the middle and the cells have been in a fixture .
Another great video, one of your best Andy.
Fixture IS important, but no, you don't have to do it. Cycle life might not be important in your high capacity installation, but most DIY installations are on a budget, and cycle way more then you do. My marine customers usually do a 600AH 12vdc installation that gets a full cycle every day or two. These installations average 250 to 300 cycles a year for my commercial customers that recharge with a diesel generator or shore power (no solar).
You brought up something I'm pretty sure I failed to mention in my previous explanations. The cells do in fact swell and compress. Like I motioned in previous comments, the major swelling you've experienced is avoidable with a fixture, it's why I said that cells should only be removed when empty. The level of swelling you've experienced is completely avoidable.
As for your statement that cells won't be damaged by compressing after they have severe swelling, my friend I encourage you to do so and see for yourself the fluid flowing out of the seal( It will make a great video =). Fluid breaking though the seal is damage. The question then becomes, how much damage can be done before cell capacity is affected? I personally have have not been willing to push past the seal breaking point after doing it the first time. If you flatten them until they are as flat as new cells will they burst and compromise the vacuum? inquiring minds want to know. Lets see that video Andy! For Science!!1
Wow, yes, that would make a great video! 😮
I have Winston cells in my RV that I assembled with significant compression, and flexible Busbars. To my knowledge they’re still virtually as good as new. Although I haven’t disassembled the pack (big job in a tight space!), nor done a full scientific capacity test, I have noticed zero problems with daily use and the occasional deeper discharge, and they are still absolutely fabulous.
I also have a friend who has “abused” his a lot more than me, with some low voltage AND high voltage “excursions”, with no BMS. They’re also still fine.
Thanks again Andy! Great information always
Thanks Joe!
Hi, I bought some 20 year old winston thundersky 60ah, Capacity is 50ah, so calendar ageing is pretty slow, they were factory compressed in 3 cell packs.
Great, hope they will still last for a while...
Once again, my knowledge has grown ten fold! You are dishing out gold nuggets free! Think it is time for another round of S.P.A.T. sponsorship!
Thanks Andy for the reassurance on my decision not to compress for my 12v 280ah pack I made. I cycle it aprox 12 times per year so it will make 0 difference for me.
Thx for the video.
I built a clamp for initial testing my cells after reading that manual - not made of out metal, but out of "18mm Siebdruckplatte", and i do not exactly compress to 300kg. Well - first cell of eight i tested without that clamp, all the other cells with clamp. And i have to admit: the first cell got a little more bloated then the others - not really exactly measured it, but you could see the slight difference. Cells were nearly perfectly flat before testing (EVE LF280K Grade A Cells from NKON).
Well another aspect: when you compress flat cells with a force of 300kg and cells will expand anyway (on that atomic level), the pressure might rise above 300kg leading to damaging the cells 🤔? Not sure about that, so i do compress my cells a little using a compressed sturdy closed foam piece that can expand when pressures rises.
The video is definetly worth watching - and stills leaves some unanswered question :). I'm curious when there will be a followup.
Thanks Andy.
I am though, going to replace the busbars with flexible cable and lugs as I do believe that there is stress on those terminals. And I dont think that will do any battery any good.
Luv ya effort.
Thanks for clearing up all that information.
Congrats! Your are the first I watch who has gotten it and explained it in a very clear way. Remains the question what would have happened to your "certified" cells which spread apart. I think it helps to keep the cells in check so no readjustment of solid bars is necessary. If you have flexible busbars then it might not matter.
So there might be a mechanical advantage to apply some pressure to the cells.
I developed a way to administer the right amount of compression to the cells with my cordless screwdriver. I didn't want to buy another tool (torque wrench) which I would use only one time. So I thought about the screwdriver I already own because its torque can be adjusted. Albeit with no calibrated settings.
To find the right setting I used bathroom scales and a lever. The lever was attached to a board at one end with a long screw. Halfways I made a hole in the lever and the board through which I put the actual threaded rod I want to use on the battery. The far end got a short screw which pressed on the scale. So I had a 1:2 ratio of the middle and the end forces. The 300kgf on the battery cells will be achieved by four tensioning rods. So a single rod has to produce 75kgf of pull. On my setup if the 75kgf have been reached at the middle of the lever the scale would show 32.5kg. I let the cordless screwdriver tighten the nut on the rod until the scale showed 30kg. Then I turned the clutch setting back until it clicked (released) at that scale reading. I marked the setting and that gave me the torque wrench setting I need.
Hello ! I have started to build my own 12v battery after I have seen all your videos from the beginning until now. It is a small project but I am learning. Congratulations for all your good work and good advices! You are the best !
Your explanation sounds solid and clear. But you state positions so strictly that i ask how can you be sure? I could imagine that a compression even after some testcycles done in the factory could still prevent damage by even more little bubbles or at least it will help get the bubbles out of the active material. To me it all sounds more like guessing and try-and-error process what treatment is most beneficial. I agree the effort of compression might not pay out over time because the cells degrade more from aging than from cycling in a typical usage.
Once you compress the cells, you keep them compressed. Nobody will take off the compression, even it is not needed any more.
@@OffGridGarageAustralia agree - but is that a problem? Its better for the capacity if the layers are kept closely together. Problem is the cell needs to 'breath' a bit, a y-bit.
But you didn't mention anything about terminal stress. Your batteries in their swelled state appeared to be put some stress on the terminals.
Also I've had my Eve 230 cells compressed since I bought them 18 months ago and I will take them apart again this weekend to check with a straight metal ruler for swelling. But I did not see any last weekend when I had them apart for reconfiguration
Almost two years ago I had a translated conversation in China with a CATL rep. I was told that the main enemy of Lifepo4 cells is moisture, and that a deep vacuum is applied to the cells prior to sealing in order to convert any moisture into a gas, remove as much moisture as possible, and that any remaining moisture in gas form was not expected to cause damage The compression I was told was to help maintain cell vacuum and keep any moisture present, no matter how little, in gas form where it will cause no damage. So, now I have even more questions. Actually, questions upon questions which lead to even more questions. Given that spent time is the only thing which we can never recover, I'm ready to move on.
Yeah- I’m sure we will know a lot more about these cells in thirty years time. Problem is: I won’t still be here 😅
It’s all still fascinating though, great stuff and great research and testing by Andy.
At least my seven plus years old LFP Winston cells are still awesome.
@@FutureSystem738 I realize that this is an old comment, but on the off chance that you may see this and reply:
I have been highly interested in these Winston cells, yet I have been unable to find much info on them in terms of real world experience. You have that, so if you might kindly answer a couple of questions I'd be greatly appreciative:
1) In what application are you using the Winston cells (ESS, EV, mobile/marine, etc.)?
2) What size cells do you have? What is your pack voltage, and in what configuration are they assembled (i.e. 16s1p, 8s3p)
What really intrigues me about them is the manufacturer's claim that the Winston batteries, due to the yttrium, can be safely charged in low temp environments that far exceed that of a typical LFP battery. Any info you can offer is greatly appreciated. Thanks in advance!
@@vastirvision My Winston cells are 400Ah cells in just a 4s (ie: 12v) configuration in my large caravan. I built the pack at the beginning of 2016, and for many years operated them without any kind of BMS, just keeping a bit of an eye on balance with individual cell voltage monitoring, and using very conservative voltages to avoid any chance of a cell going high, and typically 13.8v top of charge = 3.45v/cell. (They’re bolted in to the caravan under some degree of compression.)
I actually manually balanced them slightly maybe about three?? times.
Then I added a JK BMS a year or so ago, which keeps them extremely well balanced, usually to within 2 millivolts, and as a result I upped the top of charge to 14v = 3.5v per cell.
Although I have never FULLY capacity tested them since installing, I often discharge to about 20% and have noticed no capacity loss since the beginning of 2016.
I have about 1kW of solar, and we use them for everything including hot water, fridge, induction cooker, microwave, and even some airconditioner use (heating and cooling) when solar conditions are good. If the weather is not so good, we revert to using some LPG for hot water and cooking to reduce electrical demands.
I was not aware of any claims about charging at lower temps- have always avoided any charging if they’re close to 0 Celsius.
Firstly; thanks for your fantastic input (output?) Andy…. Secondly; I’m trying to commission (!) a 16S set of 340Ah cells before Xmas and struggling to see see through the miasma! I am now a bit more relaxed about it but there is one thing that strikes me: How does one apply 300kg of force to a battery pack?!?!?! Mine are envisaged to be organised in two rows of 8. That’s therefore 600kg over the two faces. Incredible! I had decided to use threaded bars in conjunction with flat plates of currently unknown dimension and material and spring load the bars with old engine valve springs, to prevent exponential pressure changes as the cells wax and wane, but now I’m not convinced that my springs are man enough.
Great video. Thanks for sorting that one out.
However.…., You still might want to “compress” your batterie cells for mechanical reasons. Assuming that some stationary batteries are going to be moved around, especially by DIYers, a form of mechanical fixing might be a good idea. Packed with EVA foam in between the cells, EVA foam will compress as the battery cells expand. The cells will more likely maintain their position and this will reduce the stress on the busbars and terminals.
Congratulations for the video...great information and great show 😉
Excellent excellent information. Very valuable, thank you very much.
Thanks Rob. Thought it would be interesting to extract these info from this video and share it.
Thanks for sharing Andy, now I have another channel to watch as well 🤔, you made good points. I think I like your option of spacing between cells as your busbars won't get tense by the expansion of cells. Keep the sunny side up down under!
Apart from the arguments regarding cycle and aging of the cells, would not compressing (eg fixing ) them make sense to keep the busbars in position ? Or is it actually the other way round, always leave a bit space between the cells for the ‚swelling‘ so that there is no impact on the busbars ? ( not a option in campers / boats )
The bus bars have space in them like 4-5 mm
Like Andy said, you cannot stop the expansion. Nothing on this earth can stop the expansion. So, something has to give! If the cells are compressed, I think you do more damage to the battery terminals under a tremendous amount of physical stress.
@@marlomontanaro3233 not if you've got flexible bus burs.
Flexible busbars hands down
I guess, either flexibles bars or space in between the cells to prevent any force on the terminals. Both🤔
So what you are saying is that I should compress my cells for the first couple cycles (I basically got them directly from EVE without any further charging/discharging) to press the gas bubbles out and then keep them kind of uncompressed (my chinese case has some form of compression built in(
Interesting video. Good job that my compressed cells are EVE grade a cells, from a supplier I trust. I also didn't test or charge them until they were compressed. Mine are cycled every day or two.
Keep it up brother! Very informative video! ❤
I believe that the manufacturers would be the experts on their cells. If they say it's better to compress, then that's enough for me. We all are amateurs compared to the experts that design the cells.
The think is, they don't say it's better to compress. It's just an option.
Thanks Andy - between this video and the other one you linked to, you've laid out a lot of great info. I can now see how compression won't make a difference in my use case!
Some level of battery fixing to assist prevent/reduce stress on terminals is probably worthwhile though. Or flexible busbars.
Agreed, although based upon Digital Mermaid's heat tests of rigid vs. flexible bus bars, I think the verdict is in that flexible is better all around if you're willing to put the work in to construct them.
@@paul_dz Which requires customising busbars rather than using the standard ones supplied.
Awesome information. The beer is on me! Cheers😀
But, what about the cell terminals? If the expansion pushes the cells apart by even 5mm per cell, won't that mean that a row of 8 cells has the potential to expand by around 40mm in total? Busbars with with low tolerances might therefore cause pressure on the cell terminals and damage them as a result. I think light compression (using Kapton tape perhaps) could help in this regard. It also helps keep the battery together in the event of an earthquake too. 😉 Love your show btw.
Flex busbars
That's been really interesting. Thanks for sharing. Any we have to understand, that when that another of cycles the batteries are still at 80%. No reason to throw them away if you ask me.
And I love you too, Andy😘
I just checked my Victron Connect BMV-700 [Google -> Upgrade ostrovní elektrárny 12-36kW, LiFePo4]. It let me know, that for the last 16 months (Jan-2022 I installed BMV-700) I did 13 total charge cycles. So in my case, for 2500 cycles I have to charge/discharge my cells for 256 years. Well I am fine with these numbers.😀. Thank you Andy, you are great!
Дякую. Взнав щось нове. Підписався. Дай боже здоров"я
Thank you, Andy! Especially for the Markus video link
Brilliant !! Could also be titled " The debate around A & B grade cells...and why it doesn't matter". A suggestion for follow on video. What things really matter for a long lifetime from you LPF batteries..
As others have said, the movement of uncompressed cells can cause stress on the terminals.
I setup 16 eve 280 cells uncompressed and after about 20 cycles the noticeable swelling on about half the cells (interestingly it was not even) was pushing the bottom of the cells apart due to the clamping force on the terminal.
They are now clamped with braided bars!
Separately, Mine do one full cycle per day.
If uncompressed means I only get 2500 cycles, that is under the 10year calendar life and crosses over to the point where compression could extend the useful life????
Personal experiment over a three year span:
LiPo cells not lifepo4 but close enough for the comparation.
The packs consisted of six 8Ah cells. There were two packs.
All exterior (outer) cells swollen with age and gentle, much below specifications. Cells were specified to run from 3.5v to 4.20v at 15C. I used them within the voltage range, strictly, and peak currents were below 4C, mostly below 1C.
All four cells that were on the outside of the packs are swollen, lost their capacity beyond usefulness but the interior remaining cells that were kept compressed inside are still above 80% capacity and not swollen.
I have gone through 100's of lipos cells over the years flying RC airplanes, helicopters, and FPV drone racing. Some I have flown even swelled they still continue to work I use them until they will not hold a charge swelling doesn't concern me. The only batteries I won't fly is if they were smashed up in a crash. The few I have seen catch fire while charging always were involved in a crash. Lot depends on brands not all that cost lot more made a difference. Some cheaper brands sold from hobbyking worked well others didn't .
@@Mike-01234 flying an rc with fluffy lipos and riding fluffy lipos ain't quite the same. Alright, it hurts when crashing and burning an expensive model but it hurts more when crashing and burning an EV or a house with your arse in it :)
🤔brilliantly solved Andy
Thank you for the information. Exceptionally well explained.
Danke!
You made my day !
👍👍👍👍👍👍👍👍👍👍👍
I hug my cells carefully.
Thanks a lot Juergen, appreciate your support!
Hmm, I think the unavoidable swelling you mention around @2:35 is well known. As you charge the cell expands, as you discharge the cell contracts. I think that is different from the cell gradually getting a larger "Beer Belly :)" overtime. The question is, will your cells keep expanding? A year from now, will they be even more swollen. Would be interesting if you kept records of the sizes overtime. Thanks for the video!
If they would expand more and more with time, they would also break any compression over time, as you cannot stop it...
All cells will expand at the beginning to a certain point. Only if you overcharge the cell, it will expand further.
The expert also says, don't go near the 2.5V or 3.65V mark as the cathode and also the electrolyte start decomposing which causes damage and the cell loses capacity. 2.75V - 3.55V was recommended.
@@OffGridGarageAustralia Great news! My caravan LFP cells, over 7 years old, have never been below 3 volts and been briefly above 3.5 volts maybe just two or three times in total.
Normal for my cells is 3v absolute minimum to 3.45v absolute maximum. The little you gain by going further is negligible capacity gain for much more stress.
@@FutureSystem738 It's like with our Teslas, never charged to 100% and never to 0%. Keep it in the middle and it will last a very long time.
@@OffGridGarageAustralia Totally agree Andy. 👍
Our car has been above 90% maybe three or four times, and above 95% literally NEVER.
It has also been below 20% maybe four times as well, and below 10% NEVER.
Thank you for the great in depth knowledge about batteries!
Der Drobs ist gelutscht hat mir gefallen 😂 thanks again for the valuable knowledge
Thanks, Dirk!
Graphite expansion from zero to 100% state of charge is about 11%. Graphite is about 20% of cell volume. 11% of 20% is only a bit over 1 mm thickness change on 70 mm wide cells.
Most of what folks call bloating is excessive electrolyte decomposition. It creates the gas that bloats the cell, but the real damage done is the electrolyte solvent that decomposes to hydrocarbon tars that are left behind clogging up the electrode and separator pores restricting lithium ion exchange. Overcharging is usually the most common cause of electrolyte breakdown. The cell wrap is open at terminal top end of laminate wrap so most of the gas escapes into the metal container which is what is bloating, not much bloating on actual laminate wrap.
Initial charge forming by manufacturer builds the protective SEI (Solid Electrolyte Interface) layer around negative anode graphite granules. This breaks down and consumes some of electrolyte and creates a significant amount of out gassing. The vent port is last thing placed on cell casing so most of this charge forming outgassing escapes before port seal is installed.
Normal use charging cracks some of the SEI protective shell due to graphite expansion and it is repaired on subsequent recharging. It does consume some of the electrolyte and available free lithium causing degradation of cell over time. It also thickens the SEI which increases cell impedance. It is part of normal aging process. Nothing to do with compression.
Delamination damage is mainly the separation of graphite and LFP electrode from copper and aluminum foil current collector. Chance of delamination increases when cell temp rises due to high discharge/charge currents and ambient temps. At
Always so interesting to read from you.
Thanks for a very informative post. Expands understanding of how LifePO4 works and all misconceptions/myths
Well, this is interesting as well… it’s hard to shift mindset from compression to no-compression though.
You made it clear that it’s impossible to prevent the expansion of these cells. There is no hydraulic press large enough to prevent this, right?
What I’m not quite getting though is, with all these people building packs with static compression designs and a variety of collection of cell number, wouldn’t we be hearing about static compression cases breaking? If each cell expands by a few mm, the whole pack can grow quite a bit depending on the configuration. If a 2P4S pack grows by 16mm, I doubt the steel rods holding them together would survive that, or the wood. As a matter of fact, sounds like it’d be quite dangerous! It just seems strange that we don’t hear about compression frames failing, or even signs of failure (though it’s possible I totally missed that). If that expansion is inevitable, then something in these compressed designs has to give…
Oh, no, I don't want to shift any mindsets here! This is just for pure information purposes.
And the cells will not expand by a few mm. It is less than 1mm usually, if at all. And yes, wrong compression can be in deed dangerous. The cells will eat this movement internally if the outside compression is too large. Most people use some sort of plywood or plastic for the compression, so this material is some sort of 'soft' anyway.
From a CATL datasheet :
"The cell will generate swelling force during attenuation. The swelling force of the cell at 60% SOH under the test
condition of 15mm steel plate, which is about 40000N. The customer needs to consider the reliability of structural
strength in the product design process."
I'd say yeah, that is heaps of force. If I did the maths right, thats 1100kPa or 160PSI. Likely more since I used the entire surface area of the side of the cell (280AH) since it was not indicated. Kind of crazy.
Looking at the construction of various batteries (from those with no compression, to those with squishy foam pad things, to those banded with steel and heavy steel plates at each end) I reckon I really like the idea of squishy rubber padding between the cells, with some compression from either steel banding or threaded rods. Gives some pressure, but has give too.
Only time will tell, for first hand experience for me. I've only just gotten into the LiFePO4 game.
I have six different (compressed) packs in operation. All cells are isolated, 2mm cork, 240g/m^2 waxed paper and 2mm foamed plate material. The foamed material looks best and the + - 1mm expension during charge / discharge appear perfect compensated.
My next packs will by in the same way!
well done Andy!
I retain my cells, which looks a lot like compression, because I my solar cells are mobile. and shaky moving cells is bad.
I think this is a valid case.
its so Andy !! Thanks
Andy thank you for this video!
It has really helped.
I was getting so much contradicting information and was just confusing.
This is a really solid explanation
Andy, if you were using the cells for vehicle propulsion, discharging over say 4 hrs then charging 4 hrs, again and again, then the number of cycles would be vital wouldn't it? Hence compression from day 1 seems to be best. But... as you ask, it only needs to be for a "few" cycles. Thank you for your great vids!
The reasons that you listed I would not compress a cell for. Why I would compress a cell is I don't want the terminals to be shifting in applying pressure. Just like you did when you check your battery rack you readjusted the gapping. There's two ways of doing taking yourselves apart and adjusting them every so often or just clamp them down so they don't shift.
Very interesting information like always. Thank you.
Hey Andy,
danke für deine informativen Videos! Hier kann man wirklich einiges für seine eigene PV Anlage mitnehmen.
Weiter so! 💯
Bitte nicht auf den Blödsinn von Andy hören. Der verbreitet so viel falsches, nur um Klicks zu bekommen. Es gibt sehr viele gute Gründe, die Zellen mit Kompression einzubauen. Andy hat leider wenig davon verstanden. Aber dies ist ja bei seinen Videos üblich.
Jeder lernt, manche eben nur mit Try-n-error...
Put your cell on a vibrator and any bubbles that are stuck will rise to the top 😁 Like the needle vibrator for the concrete used to remove the bubbles inside the concrete.
I'm pretty sure, none thinked about that.
Yeah, the expert said it would need a vacuum and around 400°C to remove them all but at these high temperatures the separators (PP material) will not survive.
Great Info Andy !!
Thanks Steven.
LifePo4 cell usr manual recommends a compression fixture. Why even bother to not do it? What is wrong about compression?
Nothing wrong with a fixture. Just wanted to share the information about why the cells swell and why a fixture is recommended. But not necessary.
I've only ever purchased use cells. I hope you still love me 🤣😂🤣👍🤟👌
Absolutely! ❤
I‘ll not use compression at all. The cells will survive or not. I have seen compressed cells exploded for improper charging. That is the thing to be aware of. Some ppl do not see the bms as a part of the battery and put a breaker in the wrong place or dont use a bms at all, what will kill some cells of the pack sooner or later.
My awareness will be temperature in wintertime, my battery place is an unisolated shelf outside the house, so I‘ll isolate the batteries and put some heating elements inside, to keep the cells above 5 Celsius.
Thanks for your video. We are the rare ones without compression. And what I see in many videos, they do compression without feathers, so its wrong and the force rises while charging and that is a lot.. better no compression than wrong compression.
Great video Andy. I think you should put compression on the top shelf of the battery 1.0 and leave the other two shelves without compression. In 33 years we will know which lasted longer. 😂
I think you have hit the nail on the head here.
We don’t have actual evidence of what these cells will be like in 33 years.
Everything is hypothetical.
@@chrispaul7401 Whilst different in that they have a plastic case, my Winston LFP battery in my caravan (12v/400Ah) is still absolutely fabulous after well over seven years, so that’s a great start.
Will they still be around at 30 years of age? I doubt it, but likely neither will I. 😅
Wow, another informative video.
Thanks!
Thanks for this insight, Andy! Will check out Markus' story also!
Anode builds its SEI over the first five cycles, most of it during the first couple cycles. It is the manufacturer charge forming process. This should be complete before end user receives cells.
That can’t be the hole story. Your cells are/were swelling. That should mean that they are changing within. I’m not saying it is bad, but as you noticed; It will create problems with the busbars. Did they say anything about that? ( Happy you still want me to enjoy your channel even though I do compress my cells 🤪)
Exactly, he did not present any theory that would explain what he's seen with his cells.
No words about the connection or bus bars. I guess it comes down what kind of setup you have, mobile/stationary. To be sure, you can just use flexible bars or make your own cables.
My cells are perfectly fine. The swelling is really minimal and is almost the same as brand new certified cells I have tested.
Thankyou for confirming... IT DOESN'T MATTER!! 😅😅🎉
I wonder during expansion with each cells connected with solid busbar, would there be sufficient pressure from the expansion to break or damage the positive and negative terminals
Yeah, that could be the case! When I decided to not compress, the main reason was to allow airflow and cooling. But now with all we know, it seems to be beneficial as the cells can do whatever they want and the busbars stay as they are.
Dammit, no matter how many times I watch Markus on Dominik's channel, I don't understand any German! How did you manage?
Best channel on RUclips ✅
Thanks again, MrHuber!
I have a 32AH 8S LIFEPO4 battery. Rectangular cells. Not compressed. Put in service. For the first year all was good. Then I left it alone with a trickle charger for 6 months (the BMS should have shut off the charge when fully charged). I came back and they were hugely swollen. Probably 4mm per cell. And blew apart the battery box. No apparent damage to the lugs. Can they be recompressed (to fit back in the battery box) and put back in service?
Представитель компании NKON рекомендует компрессию. Я не думаю, что может быть хуже. Или, что еще лучше, сомнительный. Я делаю компрессию с помощью двух металлических пластин и четырех 8-миллиметровых шпилек. Самоуспокоение - это здорово!
Спасибо за видео.
Олег, Украина.
Would it not be useful to "compress" cells to make sure that the busbars do not put too much stress on the terminals, or cause bad connections? Which is mitigated when you reconnect the cells, but for welded busbars this does become relevant i imagine.
Putting some isoprene between the cells does mitigate this, as the isoprene would make sure that some space is left between the cells and takes up the swelling, and keeps the cells in position with respect to the busbars.
Yeah, we have seen this EVA foam between the cells in the Seplos box. I found this to be the best solution so far.
Visualize Andy in a naval uniform running the battery room on Das Boot. :)
A dream! A room full of these batteries, right? How would we install the solar panels on the U-Boot?
@@OffGridGarageAustralia water power submerged and wind running on top.
I'm going to agree to disagree on this one. I wish I wasn't under NDA for some of these aspects, but I've seen the difference first hand in my lab which included X-Ray/Neutron imaging of the cells to determine intercalation, morphology changes and degradation processes. Look up "4D imaging of lithium-batteries using correlative neutron and X-ray tomography with a virtual unrolling technique" and search 'compression' in that article. That was a study from 2020 in Nature.
Thank you! Is a snug wooden box combined with fiberglass tape around the cells enough? Or do we absolutely need to use steel rods?
@@mrtschulias5250 Snug wooden box will do fine.
Der Drops ist gerutscht.😂😂😂😂 Ich liebe Deine Videos.
I have saw someone did that and it blowed out just like you said. I wonder if you compress will the pressure not billed up in it.
Two big questions behind : i) "How many cycles to extract all gaz bubbles vs how many cycles resseller are doing for testing". I a pretty sure the ratio is > 1... ii) If we can't avoid expension whatever compression or not, but what abbout the rate of expension with or without compression....